1. Field of the Invention
The present invention relates to a control apparatus for establishing a rotating field in a single phase AC induction motor by alternately and cyclically connecting a source of single phase AC for discrete time periods during each cycle to first and second sets of mechanically displaced windings in the motor so as to apply a partial sine wave voltage to each of the windings of the motor, to establish a magnetic field in each set of windings and wherein the resultant sum of the two magnetic fields is a rotating field which traverses the poles of the motor during each full cycle of the AC line.
2. Prior Art
The prior art includes known systems for converting a single phase input to a plural phase output. In known phase converters which are utilized with AC induction motors, the phase shift is generally accomplished through the use of inductors, capacitors, resistors, and/or combination thereof. For example, the Smith U.S. Pat. No. 2,673,954 discloses a phase converter which utilizes a capacitor to advance the phase and an inductor to retard the phase and the Hyman U.S. Pat. No. 4,103,325 discloses a single phase to three phase converter wherein an RC circuit and an operational amplifier is utilized to shift phases. The use of circuit elements such as inductors, capacitors, and resistors is a costly way of shifting phases and only approximates the desired phase shift for running and starting an AC induction motor. The Katz U.S. Pat. No. 3,991,353 discloses a method and a motor apparatus for generating high speeds by converting an input frequency to a higher output frequency. Katz does not control a standard single phase AC induction motor. The Buffington U.S. Pat. No. 3,349,316 and the Irish U.S. Pat. No. 3,959,709, both disclose converter systems which convert single phase to multiple phases. Buffington utilizes capacitors and inductors for phase shifting and Irish utilizes solid state switch means which are switched to accomplish phase shifting.